Re: [PATCH v2 2/6] mm/sparse-vmemmap: Pass @pgmap argument to memory deactivation paths

Mike Rapoport
2026-04-15T15:55:31Z

On Wed, Apr 15, 2026 at 07:14:08PM +0800, Muchun Song wrote:
> Currently, the memory hot-remove call chain -- arch_remove_memory(),
> __remove_pages(), sparse_remove_section() and section_deactivate() --
> does not carry the struct dev_pagemap pointer. This prevents the lower
> levels from knowing whether the section was originally populated with
> vmemmap optimizations (e.g., DAX with vmemmap optimization enabled).
>
> Without this information, we cannot call vmemmap_can_optimize() to
> determine if the vmemmap pages were optimized. As a result, the vmemmap
> page accounting during teardown will mistakenly assume a non-optimized
> allocation, leading to incorrect memmap statistics.
>
> To lay the groundwork for fixing the vmemmap page accounting, we need
> to pass the @pgmap pointer down to the deactivation location. Plumb the
> @pgmap argument through the APIs of arch_remove_memory(), __remove_pages()
> and sparse_remove_section(), mirroring the corresponding *_activate()
> paths.
>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>

Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> ---
> arch/arm64/mm/mmu.c | 5 +++--
> arch/loongarch/mm/init.c | 5 +++--
> arch/powerpc/mm/mem.c | 5 +++--
> arch/riscv/mm/init.c | 5 +++--
> arch/s390/mm/init.c | 5 +++--
> arch/x86/mm/init_64.c | 5 +++--
> include/linux/memory_hotplug.h | 8 +++++---
> mm/memory_hotplug.c | 12 ++++++------
> mm/memremap.c | 4 ++--
> mm/sparse-vmemmap.c | 17 +++++++++--------
> 10 files changed, 40 insertions(+), 31 deletions(-)
>
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index dd85e093ffdb..e5a42b7a0160 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -2024,12 +2024,13 @@ int arch_add_memory(int nid, u64 start, u64 size,
> return ret;
> }
>
> -void arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap)
> +void arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap)
> {
> unsigned long start_pfn = start >> PAGE_SHIFT;
> unsigned long nr_pages = size >> PAGE_SHIFT;
>
> - __remove_pages(start_pfn, nr_pages, altmap);
> + __remove_pages(start_pfn, nr_pages, altmap, pgmap);
> __remove_pgd_mapping(swapper_pg_dir, __phys_to_virt(start), size);
> }
>
> diff --git a/arch/loongarch/mm/init.c b/arch/loongarch/mm/init.c
> index 00f3822b6e47..c9c57f08fa2c 100644
> --- a/arch/loongarch/mm/init.c
> +++ b/arch/loongarch/mm/init.c
> @@ -86,7 +86,8 @@ int arch_add_memory(int nid, u64 start, u64 size, struct mhp_params *params)
> return ret;
> }
>
> -void arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap)
> +void arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap)
> {
> unsigned long start_pfn = start >> PAGE_SHIFT;
> unsigned long nr_pages = size >> PAGE_SHIFT;
> @@ -95,7 +96,7 @@ void arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap)
> /* With altmap the first mapped page is offset from @start */
> if (altmap)
> page += vmem_altmap_offset(altmap);
> - __remove_pages(start_pfn, nr_pages, altmap);
> + __remove_pages(start_pfn, nr_pages, altmap, pgmap);
> }
> #endif
>
> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
> index 648d0c5602ec..4c1afab91996 100644
> --- a/arch/powerpc/mm/mem.c
> +++ b/arch/powerpc/mm/mem.c
> @@ -158,12 +158,13 @@ int __ref arch_add_memory(int nid, u64 start, u64 size,
> return rc;
> }
>
> -void __ref arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap)
> +void __ref arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap)
> {
> unsigned long start_pfn = start >> PAGE_SHIFT;
> unsigned long nr_pages = size >> PAGE_SHIFT;
>
> - __remove_pages(start_pfn, nr_pages, altmap);
> + __remove_pages(start_pfn, nr_pages, altmap, pgmap);
> arch_remove_linear_mapping(start, size);
> }
> #endif
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index decd7df40fa4..b0092fb842a3 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -1717,9 +1717,10 @@ int __ref arch_add_memory(int nid, u64 start, u64 size, struct mhp_params *param
> return ret;
> }
>
> -void __ref arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap)
> +void __ref arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap)
> {
> - __remove_pages(start >> PAGE_SHIFT, size >> PAGE_SHIFT, altmap);
> + __remove_pages(start >> PAGE_SHIFT, size >> PAGE_SHIFT, altmap, pgmap);
> remove_linear_mapping(start, size);
> flush_tlb_all();
> }
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index 1f72efc2a579..11a689423440 100644
> --- a/arch/s390/mm/init.c
> +++ b/arch/s390/mm/init.c
> @@ -276,12 +276,13 @@ int arch_add_memory(int nid, u64 start, u64 size,
> return rc;
> }
>
> -void arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap)
> +void arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap)
> {
> unsigned long start_pfn = start >> PAGE_SHIFT;
> unsigned long nr_pages = size >> PAGE_SHIFT;
>
> - __remove_pages(start_pfn, nr_pages, altmap);
> + __remove_pages(start_pfn, nr_pages, altmap, pgmap);
> vmem_remove_mapping(start, size);
> }
> #endif /* CONFIG_MEMORY_HOTPLUG */
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index df2261fa4f98..77b889b71cf3 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -1288,12 +1288,13 @@ kernel_physical_mapping_remove(unsigned long start, unsigned long end)
> remove_pagetable(start, end, true, NULL);
> }
>
> -void __ref arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap)
> +void __ref arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap)
> {
> unsigned long start_pfn = start >> PAGE_SHIFT;
> unsigned long nr_pages = size >> PAGE_SHIFT;
>
> - __remove_pages(start_pfn, nr_pages, altmap);
> + __remove_pages(start_pfn, nr_pages, altmap, pgmap);
> kernel_physical_mapping_remove(start, start + size);
> }
> #endif /* CONFIG_MEMORY_HOTPLUG */
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 815e908c4135..7c9d66729c60 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -135,9 +135,10 @@ static inline bool movable_node_is_enabled(void)
> return movable_node_enabled;
> }
>
> -extern void arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap);
> +extern void arch_remove_memory(u64 start, u64 size, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap);
> extern void __remove_pages(unsigned long start_pfn, unsigned long nr_pages,
> - struct vmem_altmap *altmap);
> + struct vmem_altmap *altmap, struct dev_pagemap *pgmap);
>
> /* reasonably generic interface to expand the physical pages */
> extern int __add_pages(int nid, unsigned long start_pfn, unsigned long nr_pages,
> @@ -307,7 +308,8 @@ extern int sparse_add_section(int nid, unsigned long pfn,
> unsigned long nr_pages, struct vmem_altmap *altmap,
> struct dev_pagemap *pgmap);
> extern void sparse_remove_section(unsigned long pfn, unsigned long nr_pages,
> - struct vmem_altmap *altmap);
> + struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap);
> extern struct zone *zone_for_pfn_range(enum mmop online_type,
> int nid, struct memory_group *group, unsigned long start_pfn,
> unsigned long nr_pages);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 2a943ec57c85..6a9e2dc751d2 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -583,7 +583,7 @@ void remove_pfn_range_from_zone(struct zone *zone,
> * calling offline_pages().
> */
> void __remove_pages(unsigned long pfn, unsigned long nr_pages,
> - struct vmem_altmap *altmap)
> + struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
> {
> const unsigned long end_pfn = pfn + nr_pages;
> unsigned long cur_nr_pages;
> @@ -598,7 +598,7 @@ void __remove_pages(unsigned long pfn, unsigned long nr_pages,
> /* Select all remaining pages up to the next section boundary */
> cur_nr_pages = min(end_pfn - pfn,
> SECTION_ALIGN_UP(pfn + 1) - pfn);
> - sparse_remove_section(pfn, cur_nr_pages, altmap);
> + sparse_remove_section(pfn, cur_nr_pages, altmap, pgmap);
> }
> }
>
> @@ -1425,7 +1425,7 @@ static void remove_memory_blocks_and_altmaps(u64 start, u64 size)
>
> remove_memory_block_devices(cur_start, memblock_size);
>
> - arch_remove_memory(cur_start, memblock_size, altmap);
> + arch_remove_memory(cur_start, memblock_size, altmap, NULL);
>
> /* Verify that all vmemmap pages have actually been freed. */
> WARN(altmap->alloc, "Altmap not fully unmapped");
> @@ -1468,7 +1468,7 @@ static int create_altmaps_and_memory_blocks(int nid, struct memory_group *group,
> ret = create_memory_block_devices(cur_start, memblock_size, nid,
> params.altmap, group);
> if (ret) {
> - arch_remove_memory(cur_start, memblock_size, NULL);
> + arch_remove_memory(cur_start, memblock_size, NULL, NULL);
> kfree(params.altmap);
> goto out;
> }
> @@ -1554,7 +1554,7 @@ int add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
> /* create memory block devices after memory was added */
> ret = create_memory_block_devices(start, size, nid, NULL, group);
> if (ret) {
> - arch_remove_memory(start, size, params.altmap);
> + arch_remove_memory(start, size, params.altmap, NULL);
> goto error;
> }
> }
> @@ -2266,7 +2266,7 @@ static int try_remove_memory(u64 start, u64 size)
> * No altmaps present, do the removal directly
> */
> remove_memory_block_devices(start, size);
> - arch_remove_memory(start, size, NULL);
> + arch_remove_memory(start, size, NULL, NULL);
> } else {
> /* all memblocks in the range have altmaps */
> remove_memory_blocks_and_altmaps(start, size);
> diff --git a/mm/memremap.c b/mm/memremap.c
> index ac7be07e3361..c45b90f334ea 100644
> --- a/mm/memremap.c
> +++ b/mm/memremap.c
> @@ -97,10 +97,10 @@ static void pageunmap_range(struct dev_pagemap *pgmap, int range_id)
> PHYS_PFN(range_len(range)));
> if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
> __remove_pages(PHYS_PFN(range->start),
> - PHYS_PFN(range_len(range)), NULL);
> + PHYS_PFN(range_len(range)), NULL, pgmap);
> } else {
> arch_remove_memory(range->start, range_len(range),
> - pgmap_altmap(pgmap));
> + pgmap_altmap(pgmap), pgmap);
> kasan_remove_zero_shadow(__va(range->start), range_len(range));
> }
> mem_hotplug_done();
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index a7b11248b989..40290fbc1db4 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -665,7 +665,7 @@ static struct page * __meminit populate_section_memmap(unsigned long pfn,
> }
>
> static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
> - struct vmem_altmap *altmap)
> + struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
> {
> unsigned long start = (unsigned long) pfn_to_page(pfn);
> unsigned long end = start + nr_pages * sizeof(struct page);
> @@ -674,7 +674,8 @@ static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
> vmemmap_free(start, end, altmap);
> }
>
> -static void free_map_bootmem(struct page *memmap)
> +static void free_map_bootmem(struct page *memmap, struct vmem_altmap *altmap,
> + struct dev_pagemap *pgmap)
> {
> unsigned long start = (unsigned long)memmap;
> unsigned long end = (unsigned long)(memmap + PAGES_PER_SECTION);
> @@ -746,7 +747,7 @@ static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
> * usage map, but still need to free the vmemmap range.
> */
> static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> - struct vmem_altmap *altmap)
> + struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
> {
> struct mem_section *ms = __pfn_to_section(pfn);
> bool section_is_early = early_section(ms);
> @@ -784,9 +785,9 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
> * section_activate() and pfn_valid() .
> */
> if (!section_is_early)
> - depopulate_section_memmap(pfn, nr_pages, altmap);
> + depopulate_section_memmap(pfn, nr_pages, altmap, pgmap);
> else if (memmap)
> - free_map_bootmem(memmap);
> + free_map_bootmem(memmap, altmap, pgmap);
>
> if (empty)
> ms->section_mem_map = (unsigned long)NULL;
> @@ -828,7 +829,7 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn,
>
> memmap = populate_section_memmap(pfn, nr_pages, nid, altmap, pgmap);
> if (!memmap) {
> - section_deactivate(pfn, nr_pages, altmap);
> + section_deactivate(pfn, nr_pages, altmap, pgmap);
> return ERR_PTR(-ENOMEM);
> }
>
> @@ -889,13 +890,13 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
> }
>
> void sparse_remove_section(unsigned long pfn, unsigned long nr_pages,
> - struct vmem_altmap *altmap)
> + struct vmem_altmap *altmap, struct dev_pagemap *pgmap)
> {
> struct mem_section *ms = __pfn_to_section(pfn);
>
> if (WARN_ON_ONCE(!valid_section(ms)))
> return;
>
> - section_deactivate(pfn, nr_pages, altmap);
> + section_deactivate(pfn, nr_pages, altmap, pgmap);
> }
> #endif /* CONFIG_MEMORY_HOTPLUG */
> --
> 2.20.1
>

--
Sincerely yours,
Mike.